JP6630664B2 - Wind turbine control - Google Patents

Description

[Technical field]
The invention relates to the field of wind turbines.

[Background Art]
Wind turbines are an established means for power generation. Generally, wind turbines include a rotor that supports a plurality of blades. The rotor is configured to drive the generator directly or via a gearbox. In a horizontal shaft turbine, the generator housing (this housing is also called the nacelle) and the rotor are supported by a tower. The most common type is an up-wind type in which the blade faces the wind. A yaw system maintains the orientation of the rotor and blades within acceptable limits for wind direction. A turbine control system controls the speed and power of the rotor by tilting (pitching) the blades. Both yaw and pitch movements are powered by geared electric motors. Hydraulic cylinders are also commonly used to power pitch movement. On top of the nacelle is placed an ultrasonic or mechanical instrument for measuring wind speed and direction. For large wind turbines, the wind flow may not be uniform throughout the rotor passage area, so the ability to tilt the blades individually is common.

  The rotor is supported by bearings (usually rolling element bearings, sometimes referred to as low friction bearings). For large wind turbines, large-diameter slim-profile bearings tend to be used. The large diameter slim profile bearings are coaxially disposed and closely spaced from one another. Multiple bearings may be combined into a single bearing unit. The result is a compact design with high bending and torsional stiffness. Compared to traditional smaller wind turbine designs, the use of large diameter slim profile bearings imposes more complex requirements on the design and stiffness of the mating components.

  The rolling elements are preferably maintained under a sufficient contact force in order to ensure rolling contact with the bearing race. The loss of contact force can cause the rollers to begin to slide against the bearing race, which is harmful. The maintenance of the contact force is achieved by applying a high preload of the bearing during the assembly and installation process of the bearing. The preload ensures a minimum initial contact force between the stationary part of the bearing, the rolling elements and the rotating part of the bearing. The preload also avoids excessive localized contact forces in the bearing after the rotor and blades are mounted on the bearing. The contact force between the rollers and the race as a result of the resultant of the preload of the bearing and the external forces from operation presents bearing design constraints. In operation, flexing of a slim profile large diameter bearing can generate a non-uniform load profile around the diameter of the bearing. In addition, roller and race wear reduces the initial preload over time. Global and spatial variations in contact force are measured as strain variations in bearing races.

[Overview]
According to a first aspect,
A method for dynamically controlling a wind turbine, comprising:
The wind turbine has a rotor that supports a plurality of blades, and a main bearing that supports the rotor,
The method comprises:
Detecting a load profile around the circumference of the main bearing;
Generating a control signal based on the detected load profile;
Dynamically adjusting the load profile of the main bearing using the control signal.

Detecting the load profile may include detecting strain at a plurality of locations around the bearing with a fiber optic sensor.
The method further comprises:
Detecting the temperature of the bearing;
Dynamically adjusting the load in response to the detected load profile in combination with the detected temperature.

  Dynamically adjusting the load profile may include adjusting an orientation of the blades of the wind turbine in response to the detected load profile, and optionally, adjusting the orientation of the blades. Adjusting may include adjusting a pitch angle of the blade or adjusting a yaw system. Adjusting the preload profile may include applying a force to the bearing in addition to the force applied by the rotor.

  The method may further comprise storing the detected load profile of the bearing in a memory for monitoring the condition of the bearing, and optionally using the detected load profile. Monitoring the status of the wind turbine.

  The step of dynamically adjusting the load profile of the main bearing may involve a closed-loop control process using the detected load profile as an input.

According to a second aspect,
An active control assembly for controlling a wind turbine, comprising:
The wind turbine has a rotor that supports a plurality of blades, and a main bearing that rotatably couples the rotor to a housing.
The active control assembly includes:
A detector configured to detect a load profile of the main bearing;
A processor configured to determine a required adjustment of the blade in response to the detected load profile of the main bearing, and configured to generate a control signal;
An actuation mechanism for receiving the control signal, wherein the actuation mechanism is configured to adjust the load profile in response to the control signal is provided.

  The active control assembly may further include a temperature sensor configured to detect a temperature profile of the main bearing. The detector may include a fiber optic sensor. The optical fiber sensor may include a Bragg grating. The fiber optic sensor may have an outer diameter of substantially 125 μm. The fiber optic sensor may be embedded in a stationary race of the main bearing. The actuation mechanism may be configured to adjust a pitch angle of the blade.

  The actuation mechanism may include at least one piston configured to apply a force to the main bearing in addition to a force applied by the rotor. The main bearing may be a slim profile large diameter rolling element bearing.

  According to a third aspect, there is provided a wind turbine comprising an active control assembly as described above.

According to a fourth aspect,
A receiver for receiving the detected load profile of the main bearing of the wind turbine;
A processor for determining a control signal for adjusting the load profile;
A transmitter for sending commands to dynamically adjust the load profile of the main bearing;
A computing device is provided, comprising:

According to a fifth aspect,
A computer program comprising a non-transitory computer readable code, wherein the computer readable code, when executed on a computer device, causes the computer device to operate as the computer device described above. Is done.

  According to a sixth aspect, there is provided a computer program product comprising a non-transitory computer readable medium and a computer program as described above, wherein the computer program is stored on the non-transient computer readable medium. Provided.

It is a figure which shows the vertical cross section of a wind turbine schematically. It is a figure which shows the vertical cross section of a bearing schematically. FIG. 4 is a flow diagram illustrating exemplary steps for controlling a preload profile in a bearing. FIG. 2 is a block diagram schematically illustrating an exemplary computing device.

[Detailed description]
Generally, wind turbines include a rotor that supports a plurality of blades. The rotor is configured to drive the generator directly or via a gearbox. A stationary tower supports the blade, rotor, generator, and powertrain assembly. Preferably, the blades oppose the wind direction such that the plane defined by the blades is perpendicular to the wind direction. The orientation of the rotor and blades relative to the stationary tower is controlled by a yaw mechanism. The turbine control system controls the rotor speed by tilting (pitching) the blade.

  The rotor is supported by bearings. For large wind turbines, large diameter slim profile bearings may be used. The preload of the bearing can be set during the manufacturing process of the bearing. The preload prevents a loss of contact force between the stationary part of the bearing, the rolling elements and the rotating part of the bearing. The preload also avoids excessive localized contact forces in the bearing after the rotor and blade have been mounted on the bearing. The load profile of the bearing is determined by measuring the load profile of the bearing around the circumference of the bearing, then generating a control signal based on the detected load profile, and using the control signal to control the bearing. By dynamically adjusting the load profile, it can be dynamically controlled.

  The measurement may be collected by an optical fiber embedded in (or otherwise fixed to) the stationary part of the bearing. The fiber preferably surrounds the entire bearing. Roller bearing strain measurements are described by Lars Hoffmann et al in "Monitoring Roller Bearings with Fiber Optic Sensors" (Technisches Messen 74 (2007) 4, pages 204-210). The optical fiber may include one or more Bragg gratings. As light propagates through the fiber, some wavelengths are reflected by the Bragg grating and others are transmitted. When strain is applied to one region of the fiber, the refractive index changes in the strained region, and this change is detectable by a shift in the wavelength of the reflected and transmitted light. Multiple Bragg gratings may be used in a single optical fiber so that bearing strain can be measured at multiple locations around the circumference of the bearing. The load profile can be estimated using the plurality of strain measurements. Multiple fibers may be used to increase the set of measurements.

  Alternatively, conventional strain gauges other than optical fiber may be used to determine the load profile.

  Fiber Bragg grating sensors are also temperature sensitive because the optical properties of the fiber depend on the temperature of the fiber. In addition to measuring strain at multiple locations, a fiber Bragg grating may determine the temperature of the bearing at multiple locations. The strain and temperature around the circumference of the bearing are dependent on each other. For example, if the temperature increase in the outer race during operation is greater than the temperature increase in the inner race, the thermal expansion of the outer race will be greater, thereby reducing the preload. Large temperature gradients can lead to deformation of the bearing material (which leads to a change in the load profile of the bearing). Instead of using an optical fiber to determine the temperature, another temperature measuring device may be used to determine the temperature.

  The pitch angle of each blade is adjustable depending on the measured load profile around the circumference of the bearing. Changing the pitch angle of the blade changes the load from the blade to the rotor, thereby changing the load profile of the bearing. In addition to the pitch angle of the blade, the yaw angle is also adjustable. As a result of the adjustments made to the blade, the load profile in the bearing changes.

  An actuator may be provided in or adjacent to the bearing so that the load profile of the bearing can be directly adjusted depending on the measured load profile. For example, one or more hydraulic pistons may apply a uniform pressure around the circumference of the bearing or may apply a localized pressure to a particular area of the bearing. These direct actuators for adjusting the load profile may be used in addition to or instead of the indirect control provided by adjusting the pitch or yaw angle of the blade.

  A closed loop control process may be used (the purpose of this treatment is to maintain a specific load profile around the circumference of the bearing). The input to the closed loop control algorithm is the estimated load profile of the bearing. The output of the closed loop control algorithm is a control signal, which may be combined with the speed and power control functions of the turbine to adjust the pitch angle of the blade, or sent to a direct actuator.

  In large bearings, the change in load around the circumference of the bearing is greater than in small bearings, so dynamic control of the load profile of the bearing is especially important for large bearings (such as large diameter slim profile bearings) is there.

  Temperature measurements may be an additional input to the closed loop control process. The control process may compensate for uneven temperature along the circumference of the bearing (or at least to avoid overheating of the bearing). The load profile of the bearing and the temperature of the bearing are generally not independent of each other, and the control process takes into account the dependencies to ensure a stable control process.

  Measuring the load profile also allows for long-term situation monitoring and fault detection. Changes to the behavior of the bearing baseline can be used to automatically notify and alert the operator. In addition, control parameters may be set based on long-term conditions or deviations from baseline behavior (while triggering automatic adaptation in the control system in the form of another control strategy or operating mode). For example, a fiber optic sensor may detect the occurrence of a fault in the bearing, in which case, to limit the progress of the fault, thereby improving operability, and complete failure of the bearing or In order to reduce the potential for damage to other parts of the wind turbine, the control method may automatically de-rate the turbine.

  A control system may be provided locally in the wind turbine, and remote monitoring of control parameters and bearing status may be provided.

  FIG. 1 schematically shows a vertical section of a wind turbine. A tower (1) supports an assembly including a blade (2) and a main frame (3). The blade (2) extends radially outward from a hub (4) supported by a main bearing (5). The bearing is a large diameter roller bearing. The main bearing (5) may be configured as two separate bearings arranged coaxially, or the main bearing may be provided as a single unit in which the two bearings are combined. The stationary part of the bearing is mounted on the main frame (3) and the rotating part of the bearing is mounted on the hub and blades. The axis of rotation of the hub coincides with the axis of the bearing and is indicated in FIG. For each of the blades, a pitch actuator (7) is provided to adjust the pitch of the blade. The orientation of the main frame with respect to the tower is controlled by a yaw mechanism (8).

  The load profile is measured by a strain gauge along the circumference of the bearing (5). The strain gauge is not shown in FIG. 1 but is shown in FIG. The output of the strain sensor is shown in FIG. 1 as line 9 and this output is provided to a fiber Bragg grating interrogator or signal amplifier (10). The combination of the strain measurements forms the load profile. The output of the interrogator or amplifier (10) is coupled to a turbine controller (11). This output can also be coupled to a data storage and status monitor (12). The data storage and condition monitoring device is configured to monitor the long term condition of the wind turbine using the strain measurements. The data storage and condition monitor (12) may also collect data from the turbine controller (11). The turbine controller generates a control signal that depends on the load profile. The control signal is sent to the pitch actuator system (7). A cable carrying control signals is connected between the turbine controller and the pitch drive via a rotatable or wireless connection (13). To prevent the cables from becoming tangled during the rotation of the rotor, for example, a slip ring or swivel arrangement may be used as a rotatable connection. The direct actuation device may consist of a module (14) that supplies hydraulic output or power to an actuator (15) that applies a force directly to the bearing. A pitch actuator system and direct actuators are used by the turbine controller to direct the load profile towards a desired set of profiles in a closed loop system control process implemented within the turbine controller (11).

  As an example, the load profile of a large diameter bearing can be estimated by measuring, with an optical fiber, the load at about 15-20 locations evenly distributed around the circumference of the bearing. When two optical fibers are used, the number of measurement points may be larger (for example, 30). The load between the measurement points can be estimated by interpolating the data (such as taking an average value of the measurement loads at two adjacent points). In this way, a continuous profile of the load at each position along the bearing at a particular time is estimated. This load profile may be interpreted by software so that even small imbalances in the load may be detected, and may be represented visually for interpretation by an operator. In this way, a continuous load profile is estimated along the circumference of the bearing.

  FIG. 2 schematically shows a vertical section through a bearing with a strain gauge and an actuator. The bearing has an inner race (16), which is a stationary part when used in the wind turbine shown in FIG. The bearing has an outer race (17) which is a rotating part. The outer race is rotatably supported by the inner race via the rolling elements (18). In a vertical plane, the inside of the outer race (17) facing the axis of the bearing has a generally V-shaped shape. In this example, two roller bearings in a so-called "O" configuration are combined in a single bearing unit. Two sets of rolling elements (18) engage each side of the V-shaped tapered portion of the outer race. Two strain sensors are shown (optical fiber (19) with multiple Bragg grating sensors). The optical fiber is placed in a groove in the bearing race and attached to the race material so that the strain of the race can be transmitted to the fiber and made detectable by the Bragg grating. Alternatively, a plurality of strain gauges (20) may be equally spaced along the inner race of the bearing. Although FIG. 2 shows both an optical fiber (19) and a strain gauge (20), in certain embodiments, only one of these two measurement systems may be used. The inner race (16) comprises two parts (21, 22) separated by a gap (23). Each of these two parts engages one of the two sets of rolling elements (18). The two parts of the inner lace together form a V-shape, which generally corresponds to the V-shape of the outer lace. The two parts may be pressed together by a force indicated by arrow "F" in FIG. This force can be used to adjust the load profile of the bearing. This force is exerted by the block (24). The block (24) is driven by hydraulic pressure in a space (25) behind the block (24). The block is movable in a direction parallel to the axis of rotation of the bearing, indicated by arrow F in FIG. In this way, the block and the space (25) form a piston. A single annular piston may be provided around the entire circumference of the bearing, or multiple pistons may be provided around the circumference of the bearing. The piston is used to adjust the load profile depending on the estimated load profile.

  FIG. 3 is a flow diagram illustrating exemplary steps for actively controlling a load profile on a bearing. The following numbers correspond to those in FIG.

S1. Fiber optic sensors measure the load profile within the bearing at a plurality of locations around the circumference of the bearing.
S2. The measured load profile is sent as an input to a control algorithm, which generates a control signal depending on the input.
S3. A control algorithm sends a signal to the actuator to adjust the load profile.
S1. While the blade is being adjusted, the control process continuously monitors the load profile, thereby returning to step S1.

  FIG. 4 schematically shows, in a block diagram, a computer device (26) configured for controlling a load profile in a bearing. The computing device is provided with a processor (27) and a receiver (28) for receiving a signal from a fiber optic sensor to determine whether the blade pitch requires adjustment. Based on the received measurements, the processor determines how to adjust the pitch to correct the load profile. A transmitter (29) is provided to send a signal to an actuator that controls the blade pitch.

  A non-transitory computer readable medium in the form of a memory (30) usable for storing data may be provided. It may also be used to store a computer program (31) that, when executed by the processor, causes the computer device to operate as described above.

  Those skilled in the art will appreciate that various changes can be made to the embodiments described above without departing from the scope of the present disclosure. While various embodiments have been described above, those skilled in the art can readily devise other options for adjusting the load profile of the bearing in response to the detected load profile.

Claims (21)

A method for dynamically controlling a wind turbine, comprising:
The wind turbine has a rotor that supports a plurality of blades, and a main bearing that supports the rotor,
The method comprises:
Detecting a load profile around the circumference of the main bearing;
Generating a control signal based on the detected load profile;
Using the control signal to dynamically adjust the load profile of the main bearing,
Detecting the load profile, seen including detecting a distortion at a plurality of locations around said main bearing, and estimating the continuous load profile around the main bearing,
It is, in addition to the force exerted by said rotor, using a at least one piston, including methods that apply force to the main bearing to adjust dynamically the load profile of the main bearing.   The method of claim 1, wherein the distortion comprises being detected by a fiber optic sensor at the plurality of locations around the main bearing. The method further comprises:
Detecting the temperature of the main bearing;
3. The method of claim 1 or 2, comprising dynamically adjusting a load in response to the detected load profile in combination with the detected temperature.   The method of claim 1, wherein dynamically adjusting the load profile comprises adjusting an orientation of the blades of the wind turbine in response to the detected load profile. .   5. The method of claim 4, wherein adjusting the orientation of the blade comprises adjusting a pitch angle of the blade.   5. The method of claim 4, wherein adjusting the blade comprises adjusting a yaw system.   The method of any of claims 1 to 3, wherein adjusting the load profile comprises applying a force to the main bearing in addition to a force applied by the rotor.   The method according to any of the preceding claims, further comprising storing the detected load profile of the main bearing in a memory for monitoring the condition of the main bearing.   The method according to any of the preceding claims, further comprising monitoring the status of the wind turbine using the detected load profile.   10. The method according to any one of the preceding claims, wherein dynamically adjusting the load profile of the main bearing involves a closed loop control process using the detected load profile as an input. An active control assembly for controlling a wind turbine, comprising:
The wind turbine has a rotor that supports a plurality of blades, and a main bearing that rotatably couples the rotor to a housing.
The active control assembly includes:
A detector configured to detect a load profile of the main bearing;
A processor configured to determine a required adjustment of the blade in response to the detected load profile of the main bearing, and configured to generate a control signal;
An actuation mechanism for receiving the control signal, wherein the actuation mechanism is configured to adjust the load profile in dependence on the control signal;
Detecting the load profile, seen including detecting a distortion at a plurality of locations around said main bearing, and estimating the continuous load profile around the main bearing,
An active control assembly , wherein the actuation mechanism comprises at least one piston configured to apply a force to the main bearing in addition to a force applied by the rotor .   The active control assembly according to claim 11, further comprising a temperature sensor configured to detect a temperature profile of the main bearing.   The active control assembly according to claim 11 or 12, wherein the detector comprises a fiber optic sensor.   14. The active control assembly according to claim 13, wherein said fiber optic sensor comprises a Bragg grating.   The active control assembly according to claim 13 or 14, wherein the fiber optic sensor has an outer diameter of substantially 125 μm.   The active control assembly according to any one of claims 13 to 15, wherein the fiber optic sensor is embedded in a stationary race of the main bearing.   The active control assembly according to any one of claims 11 to 15, wherein the actuation mechanism is configured to adjust a pitch angle of the blade. A wind turbine comprising an active control assembly according to any one of claims 11 to 17 . A receiver for receiving the detected load profile of the main bearing of the wind turbine;
A processor for determining a control signal for adjusting the load profile;
A transmitter for sending commands to dynamically adjust the load profile of the main bearing;
The detected load profile is a continuous load profile estimated around the main bearing, the estimation is based on strain detected at multiple locations around the main bearing ,
Adjusting the load profile includes applying a force to the main bearing using at least one piston in addition to a force applied by a rotor of the wind turbine . 20. A computer program including non-transitory computer readable code, wherein the computer readable code, when executed on a computer device, causes the computer device to operate as the computer device of claim 19. Computer program. 21. A computer program product comprising a non-transient computer readable medium and the computer program of claim 20 , wherein the computer program is stored on the non-transient computer readable medium.

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